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Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. 7"#1 &" 8+9&"), 7:1 &" 8+9&")The Right to Information, The Right to LiveMazdoor Kisan Shakti Sangathan

cfJ BIS 1993

BUREAUMANAK

OFBHAVAN,

INDIAN9 BAHADURDELHI

STANDPLRDSSHAH110002

ZA-FAR MARG Price Group 5

NEW September 1993

Conductors

and Accessories

for Overhead

Lines Sectional

Committee,

ETD 37

FOREWORD This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized the Conductors and Accessories for Overhead Lines Sectional Committee had been approved the Electrotechnical Division Council. This standard was first published in 1980. In this first revision, a test pertaining analysis has been added. In addition, resonance frequency test, fatigue test, dynamic and damper efficiency test have been revised. by by

to vibration characteristic

Vibration dampers are fitted on overhead conductors and ground wires to damp the aeolian vibrations on conductors and it is imperative for vibration dampers to be effective in reducing the vibrations, that they are of correct design and manufactured properly. Since the characteristics of it is important to evaluate the vibration dampers are super-imposed on the line parameters, characteristics of vibration dampers to determine the best placement points on the conductor with respect to the suspension and tension clamp positions. While preparing this standard, Guide on conductor self Electronics Engineers. assistance has been derived from IEEE standard 563-1978 the issued by the Institute of Electrical and Damping measurement,

In this standard, shaker table method has been specified for carrying out fatigue test (see 7.5 ) on the vibration dampers. The Committee while preparing this standard took cognisance of the fact fatigue test can alternatively be done on a test span and in the country test span facilities are now being developed by many organizations. The position will, therefore, be reviewed by the Committee as and when adequate testing facilities develop in the country and a correlation between shaker table and test span methods have been established. For the purpose of deciding whether a particular requirement of this standard is complied with the final value, observed or calculated expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 Rules for rounding off numerical values ( revised ). The number of significant places retained in the rounded ofl value should be the same as that of the specified value in this standard.

1 SCOPE 1.1 This Indian Standard specifies the requirements and tests for stockbridge vibration dampers for use on overhead power lines. 2 REFERENCES 2.1 The Indian Standards given in Amlex necessary adjunts to this standard. 3 TERMINOLOGY 3.0 For the purpose of this standard, definitions shall apply. 3.1 Aeolian Vibration Ratio of node amplitude The small amplitude (0.01 to 1 diameter of conductor/ ground wire) and high frequency (3Hz to 150 Hz) vibration of conductors under tension in the vertical plane. 3.2 Amplitude The maximum displacement of the vibmting conductor from its equilibrium position. The total displacement of the conductor peak to peak is called double amplitude. 3.3 Anti-Node 3.12 Damper Anti-node of a vibrating conductor is the point where the amplitude of vibrating conductor is maximum. 3.4 Conductor Strain strain expressed as micro also known as micro strain. Dissipation Power during vibration. 3.10 Damptr Force to anti-node amplitude. the following A are 3.8 Dynamic Characteristics the relation of Damper between: The curves giving

a) The frequency and the force developed by the damper at the clamp for one millimetre double amplitude of the clamp motion: b) The frequency and the phase angle between the force and the clamp motion; and c) The frequency damper per displacement. and the power dissipated by mm double amplitude

3.9 Damping Eftlciency

The maximum dynamic force developed by the damper and transmitted to the conductor through the damper clamp during the vibration. 3.11 Damper Resonance Frequency

The frequency at which the amplitude of the damper masses are the maximum in their respective modes of vibration.

The power~dissipated 3.13 Fatigue Life

by damper

The conductor bending millimetre per millimetre, 3.5 Messenger Cable

Fatigue life is the endurance of a damper assembly when subjected to vibration continuously and uninterruptedly. It is the life of the damper assembly in cycles of vibration for a given double amplitude of the damper clamp at a specified frequency. 3.14 Node Node of a vibrating conductor is the point where the amplitude of conductor motion is minimum.

The galvanized stranded steel formed cable to which the masses are. attached at the ends and damper clamp between the masses. 3.6 Damper Clamp the damper to the conductors.

The clamp for attaching 3.7 Damper The masses cable. Masses suitably

3.15 Phase Angle The time lag of the damper force with respect to the clamp motion during vibration expressed as angle in relation to the period of vibration. t

fixed to end of the massenger

IS 9708 : 19933.16 Resonance 5.1.3 The

Resonance is a condition of a vibrating system in which the exciting frequency equal to the natural frequency.3.17 Slip Strength

characteristics dampers. 51.4 The electrically

manufacturer and energy

shall furnish damping dissipation curves of the

vibration damuer conductive.

1

assemblv

shall

be

The load applied parallel to the axis of the conductor at which the slip of the clamp does not exceed the specified permanent slip limit. 3.18 Type Tests Tests carried out to prove conformity with this standard. These are intended to prove the general qualities and design of a given type of damper. 3.19 AcceptanceTests

51.5 All parts of damper shall be either inherently resistant to the atmospheric corrosion or suitably protected against corrosion while in service. 51.6 All coatings shall be free from defects, such as cracks, shrinkages, inclusions, blowholes, etc. The inside and outside surfaces of the damper masses shall be smooth.5.1.7 All ferrous parts shall be protected by hot-dip galvanizing in accordance with IS 2629 : 1985, except for spring washers which shall be electro-galvanized in accordance with IS 1573 : 1986. 5.1.8

Tests carried out on samples taken from a lot for the purpose of acceptance of the lot. 3.20 Routine Tests

Tests carried out on all samples to check requirements which are likely to vary during production. 3.21 Tightening Torque

It shall be obligatory on the part ofmanufacturer to furnish nlacement chart giving details of recommended spacing and numb& of &rmpers to be installed. 5.2 Messenger Cable

The torque required for tightening the clamp-bolt which is to be reconmiended by the manufacturer. 4 MATERIAL 4.1 The damper mass shall be made of cast iron hot dip galvanized alloy. 4.2 The damper clamp shall be made of permanent mould cast high strength aluminium alloy conforming to A6 of IS 617 : 1975. 4.3 The messenger cable comprising of 19 strands shall be of galvanized stranded steel formed cable having a minimum wire tensile strength of 135 kg/mm. 4.4 Bolts for clamps (Part 1) : 1984. 4.5 Electrogalvanized to IS 3063 : 1972. 4.6 Plain washers 5 GENERAL REQIJIREMENTS5.1 General 5.1.1

5.2.1 The messenger cable shall comprise of high strength steel strands which shall be hot dip galvanized as per IS 4826 : 1979. 5.2.2 The steel strands of the messenger cable shall be prefomred and/or suitably protected against loosening of its strands. 5.2.3 Exposed out ends of messenger cable shall be suitably and effectively sealed to protect against corrosion. 5.3 Damper Masses

5.3.1 The damper masses shall be of cast iron hot dip galvanized. 5.3.2 The damper mass, shall be fixed permanently to the messenger cable with suitable non-ferrous sleeves or compound. 5.3.3 The damper mass shall not drop more than 5 degrees from the centre of the damper. 5.3.4 Bach damner mass shall be designed so as to avoid accumulatron of rain water. The damper mass shall be fixed so that the rain water is drained out easily. 5.4 ClampingArrangement

shall

conform

to IS 1363

spring washers shall conform

shall conform AND

to IS 2016 : 1967.

CONSTRUCTIONAL

The vibration dampers shall be of two or more resonant frequencies, as specified by the purchaser. 5.1.2 The resonant frequencies of the damper shall be fairly well spaced apart for effectively damping out aeolian vibrations over the critical range of frequencies. 2

5.4.1 Clamp of the damper assembly shall be free from sharp ends or edges, abrasions projections, etc, and shall not cause chafingordamage to the conductor during fitting or during continued operation which would produce high electrical and mechanical stresses on normal working.

IS 9708 : 1993 5.4.2 The clamp shall have sufficient grip to maintain the ~damper in position on the conductor. 5.4.3 The clamping bolts shall be provided with suitable locking devices to prevent loosening during service. 5.4.4 The damper clamp shall be capable of being removed and reinstalled on the conductor at the designed torque without damaging the fastener or the conductor surface. 5.4.5 If specified by the purchaser, the dampers shall be suitable for installation and replacement with hot line tools. 5.4.6 The mouth of the clamp shall be so shaped that the damper can hang on the conductor without the upper piece. 6 MARKING 6.1 The vibration dampers may also be marked with the Standard Mark. 6.2 The clamp shall be legibly and indelibly with the following information: 1) Indication marked 7.1.1.1 For type tests, not less than -10 samples shall be selected out of lot to be mutually decided by the manufacture and the purchaser. The samples shall be subjected to the type tests in the following manner: Test a) Visual examination b) Verification of dimensions Number of Samples 10 )

3 (same damper c) Resonance frequency test for tests d) Dynamic characteristics test c to e) e) Damping efficiency test > f) g) h) j) 1 1 1 1 (One sample from the 3 samples selected for tests mentioned at c to e) 1 k) Galvanizing/electroplating test 4 m)Magnetic power loss test Mass pull of test Clamp slip test Clamp bolt torque test Fatigue test n) Corona test p) Radio interference voltage test 7.1.1.2 Criteria for approval The testing authority shall issue a type approval certificate, if the dampers are found to comply with the requirements of the type tests. In case of failure of any~test, testing authority shall call for fresh samples not exceeding twice the number of original samples and subject them to all the tests. If in repeat test no failure occurs, the tests may be considered to have been satisfied otherwise the lot is considered to have been rejected. 7.1.1.3 Any change in design, construction, manufacturing process or material used in a damper of approved type, shall be brought~to the notice of the purchaser who may, at its discretion, call for fresh samples embodying these changes. 7.1.2 Acceptance The following Tests the acceptance (see 7.3), tests: One sample for each subconductor simultaneously

7.1.2.1 The sampling procedure and criteria of acceptance shall be as per the sampling procedure detailed in Annex B.NOTE - If tests at 7.1.2 (d), 7.1.2 (c) and 7.1.2 (f) are not carried out as type tests, they shall be carried out as acceptance tests.

10 Corona

P) Radio intkrference

IS 9708 : 1993 7.1.3 Routine The following a) Visual Test shall constitute examination the routine test: 7.5.1 For the purpose of acceptance, criteria shall be applied: the following;

(see 7.2).

7.2 Visual Examination Damper assemblies shall be visually general finish and good workmanship. 7.3 Verification of Dimensions examined for

i) There shall not be any frequency shift by more than 22 Hz at frequencies lower than 15 Hz and ?3 Hz for frequencies higher than 15 Hz; ii) The force response curve shall getterally lie within 210 percent of the force respottse curve before fatigue test; and iii) The power dissipation of the damper shall not be less than 80 percent of the same before fatigue test. 7.6 Mass Full Off Test The vibration damper which has passed the fatigue test shall be subjected to mass pull off test as given in 7.6.1. 7.6.1 Each tnass shall be pulled off in turn by fixing the mass itt one jaw attd the clamp in the other of a suitable tensile testing machine. The longitudinal pull shall be applied gradually until the mass begins to pull out of the messenger cable. The pull-off loads shall not be less than 5 kN. 7.7 Dynamic Characteristics Test

The damper shall be suitably mounted on shacker table as in 7.7 but without force/displacement transducers. The damper shall be vibrated at damper clamp atnplitude of 1 mm peak to peak. Frequency shall bc gradually varied to detertnine the resonance fTrqucttcy at which otte of the damper mass vibrates with maximum amplitude on itself, while Ihe other damper mass remains almost silent. The resonance frequency thus idetttified shall be compared with the value guaranteed by the manufacturer/supplier. The tolerattce for resonance frequency shall be +1 Hz at a frequency lower than 15 Hz and +2 Hz at a frequency higher than 1.5 Hz. 7.5 Fatigue Test The vibration damper shall bc installed on Ihe test span of at least 30 meters and tettsiotted at 25 percent with tightening torque specified by the manufacturer. The damper shall be kept mittimum three loops away from the shaker to eliminate stray signals ittlluencing damper movement. The damper shall then be vibrated cc&ttttously attd uninterruptedly at the resottant frequency to be decided by the testing authority. For dampers involvittg torsional rcsonanl frequettcies tests shall be done at torsional modes also in additiott to the highest resonant frequencies at vertical modes. The amplitude of vibration of the damper clamp shall be maintained not less than c 25/fmm, where f is the frequency in Hz. The clamp slip test as mentioned in 7.9 shall be repeated after fatigue test without retorquenittg or adjusting the damper clamp, and the clamp shall withstand a mittimum load eqttal to 80 percent of the slip strength for a t~~ittit~~umduration of one minute. After the above tests, the damper shall be removed from tltc conductor attd subjected to dynatnic characteristic test. There shall not be any major deterioratiott in the characteristics of the damper. The damper then shall be cut open attd inspected. There shall ttot be any-broken, loose or damaged part. There shall not be significant deterioralion or wear off the damper. The conductor uttder clamp shall also bc free liom any damage.

The datnper shall be suitably tnounted on a shaker capable of simulating sinusoidal vibration with continuous frequency variation. The force and the displacement shall be measured with suitable force and displacetnettl transducers. The phase angle shall be tneasured with a suitable phase meter, cathode ray oscilloscope or recorder. The speed/ frequency of shaker shall be measured with lechometer or frequency counter. The shaker shall be vibrated at 1 mm double amplitude and the various values shall be recorded as a function of frequency. The frequency range for this test shall be as follows: Condrrctor Dimneter (mm) up to 18 Above111111 10

Freqwncy (Hz)to 60

18 mm

5 to 4.5

The force versus frequency curve shall not show steep peaks at resonance frequencies and deep troughs between resonance frequencies. The resonance frequencies shall be suitably spread within the given frequency range. An ettergy balattcing computer progratnme to Abe finalized, mutually agreed between the purchaser attd the manufacturer taking into accotmt the above dynatttic characteristics of the damper, the self damping characteristics of the conductor and power included by wittd shall bc executed to satisfy necessary damping requirements. The permitted strain for conductor attd earth wire shall not be more than 2 150 microstrain and 2 300 microstraitt respectively. 4

IS 9708 : 1993

7.8 Damper 7.8.1

Efficiency

Test

Laboratory

Tesr Setup

7.8.1.1 The test setup shall be similar to as shown in Fig. 1. The test shall be conducted indoor laboratory setup with a minimum span of L = 30 m and in still air. The ambient temperature during erection and during the tests should be given. The temperature should be constant along the span and during the measurements should be the minimum and noted. During the test the tensionvariation should not exceed + 2 percent. 7.8.1.2 The conductor shall be tensioned at 25% of its nominal rated ultimate tensile strength and if necessary any other tension of interest. Before starting the conductor should be conditioned by holding it at least for 2 hours at 25% of its UTS. To minimize the termination loses at the end of the span the conductor may be terminated by a flexture member, such as a flexible cantiliver, to avoid bending the conductor through a sharp radius of~curvature where it would normally~enter the clamp. Alternatively, the conductor may be clamped solidly to the concrete terminating fixture with a heavy clamp which should be a good fit on the comluctor. 7.8.1.3 The clamp shall not be used for maintaining the conductor tension. 7.8.1.4 There shall bc no loose parts, such as suspension clamps, U-bolts, etr, on the test span. 7.8.1.5 The test conductor shall be the same or of the same basic construction as the conductor for which the dampers are to be installed. 7.8.2 Tar Procedure

7.8.2.2 The antinodal double amplitude shall be adjusted to have peak to peak value in mm equal to 751 where, f = frequency of vibration of the conductor in Hz. The antinodal amplitude shall be measured in one of the first four loops nearest the damper. 7.8.2.3 The power given to the conductor by the shaker table is equal to the power dissipated due to self-damping capacity of the conductor together with the dissipating capacity of the damper and this can be determined as follows: P=FxV where F = Force in Newtons, V = Velocity in m/s. in the equation are RMS and

The values of F and V values.

7.8.2.4 It is preferable to carry out the test in one full span. Half span can be used in case two or four dampers per span are used on both ends as mirror images. 7.8.2.5 Smaller length of spans also can be considered for the test. But the length of span should not be less than 30 m for obtaining consistent results. When smaller spans arc used the self-damping capacity of the balance length has to bc taken into account in each case. 7.8.2.6 The load cell can be calibrated by fixing a known weight (W) on the same and vibrating it with various known frequencies (f) and amplitude (y). The magnitude of force imparted by the known we~ight (W) on the load cell when vibrated can be calculated as F = 2 n2fy(w/g) where g is the acceleration due to gravity. This value can be compared with the reading on the measuring instrument and calibration curve plotted similarly the velocity can be computed from the amplitude and frequency and compared with the reading on the measuring instrument. 7.8.2.7 A minimum of six readings are taken as tunablt harmonics frequency of the span between 0.185/D to 1.295/D Hz where D is the diameter of the conductor in metres and at an antinodal double amplitudr of

7.8.2.1 The conductor (span) shall be vibrated sinusoidally by an electrodynamic shaker table through a load cell with a velocity pick up. The shaker table is vibrated through an amplifier and a function generator with high resolution so that it is possible to vibrate, at multiple of exact loops, without anyend reflections which can be cross checked with the help of a phase meter or an oscilloscope by observing if the phase angle between the force and velocity his 90 deg.SELF-DAMPING MEASUREMENTS

TEIWONING LIEWE

FIG.1 TEST SPAN ARRANGEMENT

IS 9708:199375/f where f is the frequency in Hz. However, it is preferable to record readings at each tunable harmonic frequency of the span as well as damper resonances. 7.8.2.8 Combined power dissipation (pl) of the selfdamping capacity of conductor and damper is compared with the corresponding value of wind power inputto the span PW = Pw x L where Pw is the wind power input per metre obtained from the curve (Fig. 2) and is the length of full scale span used for testing.

Relative FIG. 2 6

amplitude

Y/III

IS 9708 : 1993 7.8.2.9 If a smaller span than ~full span is used for testing, the following method has to be followed for taking into account the self damping capacity of balance length of conductor. After recording the combined power dissipation (pt) of conductor and damper for the test span the damper shall be removed. The conductor alone shall Abe vibrated at the same frequency and antinodal amplitude as in the first case and power dissipated by the conductor in the test span (PC) recorded. From the above the power dissipated by conductor per metre length and the power dissipated by dampercan be calculated as Pe = Pc/Lt and Pd = Pt - Pc_respectively where Lt is the length of test span in m. The combined power dissipation of conductor and damper for the required span length (L) can be calculated as PL = Pe x L + Pt-Pc and compared with the wind power input to the span PW = Pw x L where Pw is the wind power input for per m taken from the curve (Fig. 2). 7.8.3 Acceptance Criteria

7.8.3.1 Damper shall be qualified if in all cases the power dissipated (PL) -by the system with damper should be equal to or greater than the wind power input (PW) for acceptable damping. 7.8.3.2 For general reference purposes, a curve based on the tests conduced on ACSR conductor (54 x 3.53 Al + 7 x 3.53 Steel) is shown at Fig. 3.

4.855 83 19.864 74 73.893 18

0.058 231 0.119 609 7 0.289 581

1.85 3.7 5.6 7.5 9

0.058 231 0.116 46 0.176 266 9 0.236 1 0.283 286

0.062 95 0.132 2

34

2 4.2 6 8.2 3.8

0.188 850.258 11 0.338 31 0.044 1 0.201 447 0.113 14 0.166 82

44

1.4 6.4 3.6 5.3

11.07 102.84 44.3 75.94

7.9 Clamp

Slip Test

7.11 Galvanizing/Electroplating

Test

The damper shall be installed on the relevant conductor in a test span with a tightening torque of the bolt specified by the manufacturer. A force of 2.5 kN before fatigue test and 2 kN after fatigue test shall be applied to the clamps along the axis of the conductor and the slip on the conductor shall not exceed 1 mm after the load is removed. Sample should withstand specified value for a minute. Thereafter pulling shall continue till slipping starts. 7.10 Clamp Bolt Torque Test of the torque value failure

The dampe.r shall be. installed on a section conductor or a bar of equivalent diameter. As of 150 percent of the manufacturers specified shall be applied to the bolt. There shall be no of the component parts.

The damper shall be tested for magnetic power loss for pure sine wave current of a value which shall be specified by the purchaser. Power loss shall be determined by averaging the losses of four dampers. The damper shall not have a magnetic power loss more than 1.0 W for current 500 A/conductor Fb;v, kV and 600 A/conductor for 400 kV and

IS 9708 : 1993 7.13 Corona Test (Applicable for Dampers for Use on Transmission Lines at 400 kV and Above) The damper shall be installed ou a bar with diameter equal to conductor diameter 2 0.25 mm arranged in a bundle with sub-conductor spacing as desired by the purchaser. The sample shall then be subjected to 50 Hz phase to ground voltage, simulatingthe maximum surface gradient as obtained on the line corresponding to 80 percent of the rated line voltage. There shall be no evidence of corona on any part of the damper. The corresponding corona inception voltage shall also be recorded. 7.14 Radio Interference Voltage Test (Applicable for Dampers Use on Transmission Lines at 400 kV and Above) The test shall be conducted in accordance with IS 8263 : 1976 simulating the maximum surface voltage gradient as obtaining on the line corresponding to 1.1 times the rated phase to ground voltage. 7.15 Vibration The details Annex C. of Analysis vibration analysis are given in

ANNEXA( Clause 2.1 ) LISTIS No.

OF REFERRED

INDIAN

STANDARDS Title galvauizing on ( first revision ) iron and steel

Title Aluminium and aluminium alloys ingots and castings for general engineering purposes ( second revision ) Hexagon head bolts, screws and nuts of product grade C: Part 1 Hexagon head screws (size range M5 to M36) ( second revision ) Electroplated coatings of zinc on iron and steel ( second revision ) Plain washers ( first revision ) practice for hot- dip

1573 : 1986 2016 : 1967 2629 : 1985

4826 : 1979 4905 : 1968 8263 : 1976

Recommended

ANNEXB (Clullse 7.1.2.1

SAMPLING PROCEDURE FOR

) VIBRATION LINES DAMPERS

FOR STOCKBRIDGE OVERHEAD POWER

B-l B-l.1

SCALE Lot

OF

SAMPLING

B-l.2 The number of dampers to be selected from each lot shall depend upon the size of the lot and shall be in accordance with co1 1 and 2 of Table 1. B-1.3.1 These dampers shall be selected from the lot at random. In order to ensure the randomness of selection, procedure given in IS 4905 : 1968 may be followed. 9

All the dampers mauufactured from the same raw material under similar conditions of~productiou shall be gFouped together to constitute a lot.

and dimensional requirements and subjected to resonance frequency test. A damper failing to satisfy any of these requirements shall be considered as defective. The lot shall be considered as conforming to these requirements if the number of defectives found in the sample is less than or equal to corresponding permissible number given in co1 3 of Table 1. B-2.2 The lot which has passed the above requirements shall be further subjected to fatigue test. For this purpose, the number of dampers as given in co1 4 of Table 1 shall be taken from those examined under B-2.1 and found satisfactory. The lot shall be considered as conforming to this requirement if all the samples pass the fatigue test. B-2.3 The lot shall be considered as conforming to the requirements of this specification, if B-2.1 and B-2.2 are satisfied.

t01000

1 001 and above

B-2 NUMBER OF FOR CONFORMITY

TESTS

AND

CRlTERIA

B-2.1 The dampers selected at random according to co1 1 and 2 of Table 1 shall be examined for visual

ANNEX C ( Clause 7.15 )

VIBRATION The vibration analysis of the conductor shall be done with and without damper installed on the span, energy balance approach, taking into account the following parameters: 4 The analysis shall be done for a single conductor without armour rods for a span ranging from 100 m to 1 100 m; b) The self damping and dynamic flexural rigidity for conductor shall be experimentally determined and fUrnished by the manufacturer/ supplier; c) The aeolian vibration level of theconductor with and without damper installed at the recommended location for wind velocity ranging from 0 to 30 km/hr, predicting amplitude, frequency and vibration energy input; ANALYSIS analysis of conductor d) From the vibration without damper antinode vibration amplitude and dynamic strain levels at clamped span extremities and antinodes shall be examined to determine the lower and upper dangerous frequency limits between which the aeolian vibration levels exceed the specified limits; and From vibration analysis of conductor with damper(s) installed at the recommended location, the dynamic strain level at the clamped span extremities, damper attachment point and the antinodes as well as damper clamp vibration amplitude and antinode vibration amplitude shall be determined. The values so determined shall not exceed the specified limits.NOTE efficiency This analysis test. is an alternate to the damper

e>

10

Standard

Mark

The use of the Standard Mark is governed by the provisions of the Bureau of Indian Standards Act. 1986 and the Rules and Regulations made thereunder. The Standard Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well defined system of inspection, testing and quality control which is devised and supervised by BIS and operated by the producer. Standard marked products are also continuously checked by BIS for conformity to that standard as a further safeguard. Details of conditions under which a licence for the use of the Standard Mark may be granted to manufacturers or producers may be obtained from the Bureau of Indian Standards.

Bureau of Indian Standards BIS is a statutory institution established under the Bureau harmonious development of the activities of standardization, and attending 10 connected matters in the country. Copyright No part of these publications may be reproduced in BIS has the copyright of all its publications. the free use, in the any form without the prior permission in writing of BJS. This does not preclude such as symbols and sizes, type or grade course of implementing the standard, of necessary details, designations. Enquiries relating to copyright be addressed to the Director ( Publications ), BIS. Review of Indian Standards of Indian Standards Act, 1986 to promote marking and quality certification of goods

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed. it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of BTS Handbook and Standards Monthly Additions. Comments on this Jndian Standard may be sent to BIS giving the following reference: Dot : No. ETD 37 ( 3278 ) Amendments Amend No. Issued Since Publication Date of Issue Text Affected